August 31, 2009

When you add chamfers and fillets to a composite solid, the chamfers and fillets become sub-objects for that composite solid. As I mentioned in a previous post, you can select sub-objects using the CTRL key. As you pass the cursor over a composite solid, the chamfers and fillets highlight. You can then click to select them just as you can with solid primitive sub-objects. Unlike solid primitive sub-objects, chamfers and fillets don’t have object grips. However, they do have object properties. For example, if I press the CTRL key and select the large fillet on the air hockey paddle, the Radius property is displayed in the Properties palette. When I enter a different value, the model dynamically updates to reflect the change. After experimenting with different sizes, I’ll set the radius back to 3.

If, when you used the Fillet tool, you selected multiple edges to fillet, all of the fillets created by that single operation are treated as one object. For example, I applied the 1 unit fillet to two edges at the same time. When I pass the cursor over either fillet (with the CTRL key pressed), both are highlighted. If I change the Radius value in the Properties window, both fillets are updated.

You can edit 3D chamfers in a similar way. When you CTRL-select a chamfer, the Properties palette displays the First Distance and Second Distance.

I could, for example, change the second chamfer distances in the air hockey paddle to 6 making a larger cut into the bottom face.

In addition to changing the fillet and chamfer values you can also remove fillets and chamfers. For example, I decided I don’t want a chamfer on the bottom of the air hockey paddle. I can use CTRL-select to select the chamfer and then use the Erase tool to remove it.

August 29, 2009

For a live, fast-paced journey into AutoCAD’s world of 3D, join me online for a free Webcast. You’ll learn how to take your design ideas from concept to completion by creating and editing solid primitive objects and smooth free-form shapes. Control selection and editing with sub-object selection filters and 3D gizmos. In addition to exploring these basic 3D tools, you’ll discover valuable tips and tricks for navigating and visualizing your 3D AutoCAD model.

August 28, 2009

In my last post I described how you can use the Chamfer command (the same one you use in 2D) to create chamfered edges on 3D models. But what if you want to create rounded edges on your 3D model? Use the Fillet tool… the same one you use for 2D design! Don’t you just love when things make sense? You can access the Fillet tool from the Modify panel of the Home tab. It’s in the same button flyout at the Chamfer tool so if you used the Chamfer tool last, you’ll have to open the flyout to access the Fillet tool.

After launching the Fillet tool, you select the 3D object you want to fillet. It doesn’t matter where you select the object because you’ll be prompted to select the edges you want to fillet later. First, however, it prompts for a fillet radius. I entered a value of 1 to create fillets on the air hockey paddle and I selected the two edges highlighted in the following image.

If you want to create additional fillets at a different radius, you’ll need to repeat the Fillet command (just as you do in 2D design). For the air hockey paddle, I’ll repeat the Fillet command using a radius value of 3 and selecting the edge as shown in the image below.

The resulting model has smooth edges. The fillets and chamfer (from my previous post) are embedded in the composite solid. Fortunately, they are still editable. That’s e-d-i-t-a-b-l-e not edible (although I guess you could argue that some fillets are edible). In my next post I’ll show you how to edit fillets and chamfers. Any guesses?

August 27, 2009

All the objects we’ve used to create our air hockey paddle are basic primitive shapes; cylinders, sphere, and cone. It conveys the general shape that we want, but the edges are hard. We’ll soften the bottom edge by adding a chamfer. You can use the same Chamfer command that you’ve probably been using for using for 2D design. When the 3D modeling workspace is active, you’ll find the Chamfer tool in the Modify panel of the Home tab. It’s in the same button flyout as the Fillet tool. Whichever one you use last will be displayed on top.

When you launch the Chamfer command, select the edge you want to chamfer. AutoCAD will highlight one of the surfaces adjacent to the selected edge. If it has highlighted the edge you want to use as the base surface, you can select OK. If you want to use a different surface as the base, you can choose Next. AutoCAD will cycle through the adjacent surfaces, highlighting each one, until you choose. For example, when I select the bottom edge of the air hockey paddle, AutoCAD highlights the circular face.

If I choose Next, AutoCAD highlights the cylindrical face. Choosing next again cycles back to the circular face.

In this particular case it doesn’t matter which one I choose as the base surface as long as I enter the appropriate values for the following prompts. I’ll go ahead and accept the bottom circular face as the base surface. AutoCAD will then prompt for the base surface chamfer distance (i.e. the distance that will be trimmed off the edge of circular face). I’ll enter a value of 2. It then asks for the other surface chamfer distance (i.e. the distance that will be trimmed off the edge of the cylindrical face). Even though I selected my chamfer edge at the beginning of the chamfer operation, AutoCAD prompts me to select it again at the end. It seems a little strange but at this point you also have the opportunity to choose the Loop option, which selects all the edges on the base surface. Since by base surface is a circular shape, there is only one edge. Below is a side view of the resulting chamfer.

If I had entered the values in a different order (1 for the base distance and 2 for the other distance) or if I had specified the cylindrical face as the base surface, the chamfer would have been 1 unit along the bottom and 2 units along the side.

August 26, 2009

I’ll continue editing the composite solid by moving and resizing the sphere. Pressing the CTRL key, I’ll select the sphere. A red, green, and blue gizmo displays at the center of the sphere. I’ll talk more about the gizmo in future posts but for now I’ll ignore the gizmo and select the sphere’s center grip.

Even if the gizmo functionality is turned off, the sphere’s center grip displays and behaves as you expect from your 2D experience with grips. Selecting the grip makes it hot and automatically enables Move editing mode. You can then select an OSNAP point on an existing object; such as the Center of the top of the cylinder.

The sphere automatically moves to that location. Selecting one of the sphere’s quadrant grips enables you to modify the sphere’s radius. You can snap to the quadrant OSNAP of the cylinder to automatically match the cylinder’s radius. Just like editing a circle in 2D right?

To verify that you snapped to the right point, thus creating a sphere with the correct radius, you can view the sphere properties in the Properties palette. The radius should equal 13 just like the cylinder radius we edited in the previous post.

August 25, 2009

In a previous post I used the Union and Subtract tools to create a composite solid from primitive objects. Even though this process produced a single object, I can still edit the primitive sub-objects within the composite solid. The key is control… or I should say CTRL is the key! If you hold down the CTRL key as you pass the cursor over the composite solid, AutoCAD highlights each sub-object.

You can then click to select the highlighted sub-object. Once it’s selected, you can use grips or the Properties palette to edit the primitive properties in the same you that you could before performing the Union or Subtract operation. For example, if you want to shorten the handle on the air hockey paddle, you might select the stretch grip and move it down 15 units. Notice the edit only affects the cylinder. In AutoCAD there are no constraints between 3D shapes (unlike parametric 3D design applications such as Inventor and Revit).

As I mentioned, you can also edit sub-objects using the Properties palette. Notice that even though the cylinder is a sub-object in the composite solid, all the typical cylinder properties are available for editing. I’ll change the radius of the cylinder to 13 and the height to 34.

August 24, 2009

As you create 3D models in AutoCAD, you’ll discover that it can be difficult to visualize the geometry using the default wireframe visual style. Visual Styles were introduced in AutoCAD 2007 and are a powerful replacement for the old “shade modes”. AutoCAD includes five visual styles: 2D Wireframe, 3D Hidden, 3D Wireframe, Conceptual, and Realistic. You can access Visual Styles in the View panel of the Home tab when the 3D modeling workspace is active.

I won’t go into detail about visual styles during this series because you can accomplish most modeling tasks using the default visual styles. I’ll throw in a few quick tips along the way as they apply to what I’m doing but I definitely encourage you to learn more about visual styles. The AutoCAD Help system is a great resource. Here are some brief descriptions of the five predefined visual styles (directly from Help system):

2D Wireframe. Displays the objects using lines and curves to represent the boundaries. Raster and OLE objects, linetypes, and lineweights are visible.

3D Wireframe (upper left in the illustration). Displays the objects using lines and curves to represent the boundaries.

Realistic (lower left). Shades the objects and smooths the edges between polygon faces. Materials that you have attached to the objects are displayed.

Conceptual (lower right). Shades the objects and smooths the edges between polygon faces. Shading uses the Gooch face style, a transition between cool and warm colors rather than dark to light. The effect is less realistic, but it can make the details of the model easier to see.

I often switch between the 2D Wireframe visual style and the Conceptual visual style as I’m creating my model. Viewing the model as a wireframe can be helpful if you want to see geometry that would otherwise be obscured by shaded faces. Viewing the model with shading, like with the Conceptual visual style, can help you better understand the model. For example, if you view the air hockey paddle in wireframe mode, you can’t tell if the cone is an extra object that overlaps the cylinders or if it has been removed from the cylinder. Changing to the Conceptual visual style, it becomes clear that the cone has been subtracted.

August 21, 2009

After a long break this summer, I’m excited to continue my AutoCAD 3D Conceptual Design series. I hope you’ve had the chance to follow along as I step through the process of designing an air hockey paddle. Keep in mind that these postings aren’t so much about creating the air hockey paddle as they are about learning the variety of tools and techniques that enable you to take your ideas from concept to completion all within the familiar AutoCAD design environment. You can apply the ideas you learn from these postings to any 3D conceptual designs in any industry.

To refresh your memory (and mine) about what I already covered, here are links to the previous postings:

In the previous postings, I created all of the basic primitive objects to create the air hockey paddle. Most of the primitive objects, such as the sphere and cylinders, represent material (mass) that I want to add to the paddle. The cone primitive, however, represents material that I want to remove from the paddle.

To add and remove solid objects, you can use Boolean tools. You’ll find these tools on the Home tab of the ribbon when the 3D Modeling workspace is active.

The Union tool joins the selected solid objects into a single composite solid object. The Subtract tool removes selected objects from other selected objects; also forming a composite solid. The order in which you perform a combination of Union and Subtract operations can create different results. For example, if I union the cylinders and sphere for the air hockey paddle and then subtract the cone, I get a big gap between the upper part of the model (the handle) and the lower part of the model (the striker). This is still a single composite solid but it looks like two separate objects, which isn’t the result I’m looking for.

The solution is easy. It’s just a matter of changing the order of my Boolean operations and the objects that I select. I can use UNDO (just as you would expect) to return to a previous state where each of the primitives are separate objects.

When using the Subtract tool, it’s important to read the command prompts to ensure you are selecting objects in the appropriate order. You must first select the objects you want to subtract from and then select the objects you want to subtract from them. For example, if I want to subtract one of these cylinders from the other, the results vary depending if I first pick the cylinder on the left or the cylinder on the right.

In this example I only selected on object to subtract from and one object to subtract from it. You can, however, select more than one object to subtract from or to subtract from them. For example, I could select box and the cylinder (below) as the objects to subtract from then select the sphere and the cone as the objects to subtract from them. The result is shown.

Since you can select multiple objects, you must remember to press enter to finish the “select from” option before you select the object(s) you want to subtract from them. This may seem obvious but, speaking from experience, it’s easy to make a mistake with the selections if you’re new to the Subtract tool or if you haven’t used it for a while because this is one of the few AutoCAD commands that prompts for two selection sets.

Okay, back to the air hockey paddle… I’ll use the Subtract tool to first subtract the cone from the lower cylinder and then I’ll union the newly created composite solid with the remaining cylinder and sphere. This is the result I was looking for!

Key concepts:

The Union tool combines selected solids to create a composite solid.

The Subtract tool removes solids from selected solids to create a composite solid. It requires two selection sets: Objects to subtract from and Objects to subtract from them.

August 20, 2009

Wow! It’s hard to believe summer is nearly over! During the past few months I was fortunate enough to enjoy another Autodesk Sabbatical. Sorry I just disappeared like that! Things were pretty busy right up until I started sabbatical and they seemed to get even busier as I caught up on my personal life. I spent most of my summer close to home (in Colorado)… camping, hiking, and working around the house. I ended sabbatical with wonderful family vacation in Hawaii… snorkeling, boogie-boarding, hiking, spelunking through lava tubes, swimming with turtles, eating shave ice, watching lava flow… I’ve never seen anything more beautiful than the views while hiking along the Na Pali coast on Kaua’i. It's postcard perfect in every direction.

Needless to say my mind hasn’t been on AutoCAD. But, I've spent this week dusting off the cobwebs and catching up on email so stay tuned as I continue my 3D Conceptual Design series!